Signal processing device and signal processing method

Abstract

A signal processing device (300A, 300B, 300D) comprises: a signal extraction unit (310A) that extracts a first pulse signal from a received signal of a first antenna (101), to which a radio wave has been input, and that extracts a second pulse signal from a received signal of a second antenna (102), which is disposed at a distance from the first antenna (101) and to which a radio wave has been input; and a signal combination unit (320A) that generates a first combined signal in which a plurality of first pulse signals are combined in a time axis direction and a second combined signal in which a plurality of second pulse signals are combined in the time axis direction.

Description

Signal processing device and signal processing method

[0001] The present disclosure relates to a signal processing device and a signal processing method.

[0002] Conventionally, a device has been disclosed that uses an array antenna to estimate the direction of arrival of an incoming radio wave based on correlation information of the incoming radio wave (see, for example, Patent Document 1). The device described in Patent Document 1 converts the outputs from the antenna elements of the array antenna that receive the incoming radio wave into digital received signals using an A / D converter, and estimates the direction of arrival of the incoming radio wave based on the converted received signals.

[0003] International Publication No. 2019 / 030857

[0004] However, in order to obtain a sufficient accuracy in estimating the direction of arrival of radio waves, the pulse width of the pulse signal output from the antenna element needs to be sufficiently larger than the sampling period of the A / D converter. For this reason, the device described in Patent Document 1 has a problem in that it is difficult to obtain a sufficient accuracy in estimating the direction of arrival of radio waves when, for example, the pulse width of the pulse signal is on the same order as the sampling period of the A / D converter.

[0005] The present disclosure is intended to solve the above-mentioned problems, and has an object to provide a signal processing device and a signal processing method that can improve the accuracy of estimating the direction of arrival of radio waves compared to conventional methods.

[0006] The signal processing device according to the present disclosure is characterized by including a signal extraction unit that extracts a first pulse signal from a signal received by a first antenna to which radio waves are input, and extracts a second pulse signal from a signal received by a second antenna that is disposed at a distance from the first antenna and to which radio waves are input, and a signal combining unit that generates a first combined signal in which a plurality of first pulse signals are combined in the time axis direction, and a second combined signal in which a plurality of second pulse signals are combined in the time axis direction.

[0007] A signal processing device according to the present disclosure extracts a first pulse signal and a second pulse signal from a first antenna and a second antenna, respectively, and generates a first combined signal in which a plurality of first pulse signals are combined in the time axis direction and a second combined signal in which a plurality of second pulse signals are combined in the time axis direction. As a result, when estimating the arrival direction of radio waves based on the first combined signal and the second combined signal, it is possible to improve the accuracy of estimating the arrival direction of radio waves compared to estimating the arrival direction of radio waves without generating the first combined signal and the second combined signal.

[0008] 5A is a schematic diagram showing a pulse signal extracted in any information transmission system by a signal extractor according to the first embodiment, and FIG. 5B is a schematic diagram showing a combined signal generated based on the pulse signal by a signal combiner according to the first embodiment. FIG. 5B is a schematic diagram showing a process performed by the radio wave direction estimation system according to the first embodiment when compressing and restoring information by sequential calculation using PAST. FIG. 5C is a flowchart showing an example of a process performed by the second control unit according to the first embodiment. FIG. 5D is a block diagram showing a schematic configuration of a radio wave direction estimation system according to a third embodiment. FIG. 5E is a block diagram showing a schematic configuration of a radio wave direction estimation system according to a fourth embodiment.

[0009] Hereinafter, embodiments according to the present disclosure will be described in detail with reference to the drawings. Embodiment 1. First, with reference to FIG. 1, a schematic configuration of a radio wave arrival direction estimation system 1 according to embodiment 1 will be described. FIG. 1 is a block diagram showing a schematic configuration of the radio wave arrival direction estimation system 1 according to embodiment 1. The radio wave arrival direction estimation system 1 is a system for estimating the arrival direction of input radio waves. As shown in FIG. 1, the radio wave arrival direction estimation system 1 includes an array antenna 100, an analog-to-digital converter (hereinafter referred to as ADC) 200, a first control unit 300A, and a second control unit 500A, which are connected to each other via signal lines so that information can be transmitted between them.

[0010] The array antenna 100 converts input radio waves into analog signals. The array antenna 100 has M antenna elements consisting of a first antenna 101, a second antenna 102, ..., an Mth antenna 10M. In the first embodiment, M represents a preset integer of 3 or greater. The first antenna 101, the second antenna 102, ..., the Mth antenna 10M are arranged at a distance from each other. For example, the first antenna 101, the second antenna 102, ..., the Mth antenna 10M are arranged at a distance from each other on a straight line, a flat surface, or a curved surface. Furthermore, for example, the first antenna 101, the second antenna 102, ..., the Mth antenna 10M are arranged at equal intervals on a straight line. Note that various types of antennas, such as dipole antennas, slot antennas, and microstrip antennas, can be used as the antenna elements of the array antenna 100.

[0011] The array antenna 100 converts the input radio waves into analog received signals for each antenna element. For example, the array antenna 100 performs amplification, filtering, frequency conversion, etc. on the input radio waves for each antenna element to convert them into received signals for each antenna element. The array antenna 100 outputs the received signals for each antenna element obtained by converting the radio waves to the ADC 200.

[0012] The ADC 200 converts an analog signal input from the array antenna 100 into a digital signal. The ADC 200 has M ADCs, each consisting of a first ADC 201, a second ADC 202, ..., and an MADC 20M, corresponding to each antenna element of the first antenna 101, the second antenna 102, ..., and the Mth antenna 10M. The first ADC 201, the second ADC 202, ..., and the MADC 20M convert the analog received signals input from the first antenna 101, the second antenna 102, ..., and the Mth antenna 10M into digital received signals for each antenna element. For example, the first ADC 201, the second ADC 202, ..., and the MADC 20M each sample the analog received signals at a preset sampling frequency, thereby converting the analog received signals into digital received signals. The ADC 200 converts the analog received signals into digital signals, and outputs the digital received signals to the first control unit 300A.

[0013] The first control unit 300A as a signal processing device includes a signal extraction unit 310A, a signal combination unit 320A, and a compression unit 330A. The signal extraction unit 310A extracts a pulse signal of a desired radio wave (hereinafter referred to as a desired wave) for which a direction is to be estimated, which is input to the array antenna 100, from the received signal input from the ADC 200. The signal extraction unit 310A includes M signal extraction units, each consisting of a first signal extraction unit 311A, a second signal extraction unit 312A, ..., an M-th signal extraction unit 31MA, which correspond to the first ADC 201, the second ADC 202, ..., the M-th ADC 20M, respectively. The first signal extraction unit 311A, the second signal extraction unit 312A, ..., the Mth signal extraction unit 31MA extract pulse signals of desired waves input to the first antenna 101, the second antenna 102, ..., the Mth antenna 10M from the received signals from the first ADC 201, the second ADC 202, ..., the Mth ADC 20M, respectively. For example, the first signal extraction unit 311A ​​extracts the pulse signal of the desired wave input to the first antenna 101 from the first received signal from the first ADC 201, and the second signal extraction unit 312A extracts the pulse signal of the desired wave input to the second antenna 102 from the second received signal from the second ADC 202.

[0014] Furthermore, for example, the first signal extraction unit 311A, the second signal extraction unit 312A, ..., the Mth signal extraction unit 31MA extract pulse signals of the radio waves input to the first antenna 101, the second antenna 102, ..., the Mth antenna 10M by removing interference waves and noise contained in the received signals from the first ADC 201, the second ADC 202, ..., the Mth ADC 20M, respectively. The signal extraction unit 310A outputs each of the extracted pulse signals to the signal combination unit 320A.

[0015] The signal combining unit 320A is configured to generate a combined signal by combining multiple pulse signals input from the signal extracting unit 310A. The signal combining unit 320A has M signal combining units made up of a first signal combining unit 321A, a second signal combining unit 322A, ..., an Mth signal combining unit 32MA, which correspond to the first signal extracting unit 311A, the second signal extracting unit 312A, ..., an Mth signal extracting unit 31MA, respectively. The first signal combining unit 321A, the second signal combining unit 322A, ..., an Mth signal combining unit 32MA generate combined signals by combining multiple pulse signals from the first signal extracting unit 311A, the second signal extracting unit 312A, ..., an Mth signal extracting unit 31MA in the time axis direction.

[0016] For example, the first signal combining unit 321A generates a first combined signal by combining N first pulse signals extracted by the first signal extracting unit 311A ​​in the time axis direction, and the second signal combining unit 322A generates a second combined signal by combining multiple second pulse signals extracted by the second signal extracting unit 312A in the time axis direction. In the first embodiment, N represents a predetermined integer of 2 or greater. As a result, the first signal combining unit 321A, the second signal combining unit 322A, ..., the Mth signal combining unit 32MA each generate a combined signal, which is a pulse signal obtained by multiplying the pulse width of each of the pulse signals extracted by the first signal extracting unit 311A, the second signal extracting unit 312A, ..., the Mth signal extracting unit 31MA by N. The signal combining unit 320A outputs each of the generated combined signals to the compression unit 330A.

[0017] In this way, in the radio wave arrival direction estimation system 1, M information transmission systems are formed for each of the first antenna 101, the second antenna 102, ..., the Mth antenna 10M, and the array antenna 100, the ADC 200, the signal extraction unit 310A and the signal combining unit 320A are configured to perform each processing for each of these information transmission systems.

[0018] The compressor 330A compresses the combined signal, which is information input from the signal combiner 320A. For example, the compressor 330A compresses the number of information transmission paths formed by the array antenna 100, the ADC 200, the signal extractor 310A, and the signal combiner 320A from M to K. In other words, the compressor 330A compresses the number of information transmission paths of the combined signal input from the signal combiner 320A from M to K. In the first embodiment, K represents a preset integer of 2 or greater that is smaller than M.

[0019] Specifically, the compressor 330A compresses the number of information transmission systems using PAST (Projection Approximation Subspace Tracking), which is a system number reduction algorithm. The compressor 330A outputs information obtained by compression to the second control unit 500A. For example, the compressor 330A outputs K pieces of information corresponding to M combined signals obtained by compression using PAST and matrix value data indicating the correlation between these K pieces of information to the second control unit 500A.

[0020] The second control unit 500A as a signal processing device includes a restoration unit 510A and a direction estimation unit 520A. The restoration unit 510A as a signal acquisition unit restores information input from the compression unit 330A via a signal line L1 connecting the first control unit 300A and the second control unit 500A, thereby acquiring the combined signal generated by the signal combination unit 320A. For example, the restoration unit 510A restores the combined signal generated by the signal combination unit 320A, which has M information transmission paths, based on information input from the compression unit 330A indicating that there are K information transmission paths. Specifically, the restoration unit 510A restores the number of information transmission paths by PAST. The restoration unit 510A outputs the information obtained by the restoration to the direction estimation unit 520A.

[0021] The direction estimation unit 520A estimates the direction of arrival of the desired wave, i.e., the azimuth of the source of the desired wave relative to the array antenna 100, based on the information input from the restoration unit 510A. In other words, the direction estimation unit 520A estimates the direction of arrival of the desired wave based on the phase of each combined signal input from the restoration unit 510A. For example, the direction estimation unit 520A estimates the direction of arrival of the desired wave using ESPRIT (Estimation of Signal Parameters Via Rotational Invariance Techniques), which is a direction estimation algorithm.

[0022] Next, the hardware configuration of the first control unit 300A will be described with reference to Figures 2 and 3. Figure 2 is a diagram showing an example of the hardware configuration of the first control unit 300A, and Figure 3 is a diagram showing an example of the hardware configuration of the first control unit 300A that is different from that shown in Figure 2. For example, as shown in Figure 2, the first control unit 300A is a computer having a processor 300a, a memory 300b, and an I / O port 300c, and is configured so that the processor 300a reads and executes a program stored in the memory 300b.

[0023] 3, the first control unit 300A is a computer having a processing circuit 300d, which is dedicated hardware, and an I / O port 300c, and executing a program. The processing circuit 300d is configured, for example, by a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a combination thereof. Each function of the first control unit 300A is realized by the processor 300a or the processing circuit 300d, which is dedicated hardware, executing a program. Note that the hardware configuration of the second control unit 500A is similar to that of the first control unit 300A, and therefore a description thereof will be omitted.

[0024] Next, the processing performed by the first control unit 300A will be described with reference to Figures 4 to 6. Figure 4 is a flowchart showing an example of the processing performed by the first control unit 300A. As shown in Figure 4, when the first control unit 300A starts the processing, it first acquires digital signals from multiple systems (step ST11). In this processing, the first control unit 300A acquires received signals, which are digital signals, for each information transmission system using the ADC 200.

[0025] After the process of step ST11, the first control unit 300A extracts pulse signals from the digital signals of the multiple systems (step ST12). In this process, the first control unit 300A extracts pulse signals from the received signals for each information transmission system acquired by the ADC 200 using the signal extraction unit 310A.

[0026] After the process of step ST12, the first control unit 300A generates a combined signal for each system (step ST13). In this process, the first control unit 300A generates a combined signal based on the pulse signal for each information transmission system using the signal combining unit 320A.

[0027] 5A is a schematic diagram showing a pulse signal P1 extracted by the signal extraction unit 310A in one of the information transmission systems in step ST12, and FIG. 5B is a schematic diagram showing a combined signal PA generated by the signal combination unit 320A based on the pulse signal P1 in step ST13. As shown in FIGS. 5A and 5B , in the processing of step ST13, the signal combination unit 320A generates a combined signal PA, which is a signal obtained by combining, in the time axis direction, multiple (N) pulse signals P1 acquired by the signal extraction unit 310A in each information transmission system. The combined signal PA is a signal whose length in the time axis direction is N times the pulse width W1 of the pulse signal P1.

[0028] Generally, when analog signals from multiple antenna elements receiving radio waves are sampled and converted into multiple digital signals, pulse signals corresponding to desired waves are extracted from the multiple digital signals for each antenna element, and the direction of arrival of the desired waves is estimated using a direction estimation algorithm based on these pulse signals, in order to obtain sufficient estimation accuracy, the length of the extracted pulse signals in the time axis direction (pulse width) must be sufficiently longer than the sampling period used to sample the analog signals. However, since the sampling period cannot be set arbitrarily small, depending on the performance of the analog-to-digital converter, the output time of the desired wave, or the radio wave reception environment, the length of the extracted pulse signals in the time axis direction may not be sufficiently longer than the sampling period.

[0029] In contrast, the radio wave arrival direction estimation system 1 according to the first embodiment is configured to estimate the arrival direction of radio waves based on a combined signal generated by the signal combining unit 320A of the first control unit 300A. The combined signal generated by the signal combining unit 320A has a longer length in the time axis direction than the pulse signal extracted by the signal extracting unit 310A. Therefore, the radio wave arrival direction estimation system 1 according to the first embodiment can improve the estimation accuracy of the arrival direction of radio waves compared to a case in which the arrival direction of radio waves is estimated based on the pulse signal extracted by the signal extracting unit 310A without generating a combined signal. In other words, the radio wave arrival direction estimation system 1 according to the first embodiment can obtain sufficient estimation accuracy of the arrival direction of radio waves, regardless of the pulse width of the extracted pulse signal, by generating a combined signal of a sufficient length according to the sampling period.

[0030] It is desirable that the value of N described above be set so that the length in the time axis direction of the combined signal PA generated by the signal combining unit 320A is a length that allows sufficient estimation accuracy to be obtained in the estimation by the direction estimation unit 520A. For example, in estimation by the direction estimation unit 520A using a direction estimation algorithm such as ESPRIT, it is desirable that the length in the time axis direction of the combined signal PA is a length that allows a sufficient number of sampling points (e.g., approximately 1000 points) required for calculating the correlation matrix to be obtained.

[0031] After performing the process of step ST13, the first control unit 300A compresses the number of systems and outputs the signal (step ST14). In this process, the first control unit 300A compresses the number of information transmission systems of the combined signal, which is the information input from the signal combining unit 320A, and outputs the information obtained by the compression to the second control unit 500A. In other words, in this process, the first control unit 300A compresses the information so as to reduce the number of information transmission systems (number of channels) of the combined signal, which is the information input from the signal combining unit 320A, and outputs the information obtained by the compression as a digital signal to the second control unit 500A.

[0032] 6 is a schematic diagram showing the process when the radio wave arrival direction estimation system 1 compresses and restores information by sequential calculation using PAST in step ST14. FIG. 6 shows that the number of elements in the information transmission system is compressed from M before processing to K. Note that the compression of information by the compression unit is not limited to using PAST. The compression of information by the compression unit may be lossless compression, and may use a compression algorithm other than PAST.

[0033] Next, the processing performed by the second control unit 500A will be described with reference to Fig. 7. Fig. 7 is a flowchart showing an example of the processing performed by the second control unit 500A. As shown in Fig. 7, when the second control unit 500A starts the processing, it first acquires a signal with a compressed number of systems (step ST21). In this processing, the second control unit 500A acquires, from the first control unit 300A, a digital signal including information on a plurality of combined signals as information compressed by the compression unit 330A of the first control unit 300A.

[0034] After the processing of step ST21, the second control unit 500A restores the number of signal systems (step ST22). In this processing, the second control unit 500A restores the signal input from the first control unit 300A using the restoration unit 510A in a manner corresponding to the information compression method used by the compression unit 330A, thereby obtaining the combined signal before compression by the compression unit 330A. For example, if the information compression by the compression unit 330A is performed using PAST, the restoration unit 510A restores the information using PAST, as shown in FIG. 5.

[0035] After performing the processing of step ST22, the second control unit 500A estimates the arrival direction of the radio wave (step ST23). In this processing, the second control unit 500A estimates the arrival direction of the desired wave using the direction estimation unit 520A based on the multiple combined signals restored by the restoration unit 510A. For example, the second control unit 500A estimates the arrival direction of the desired wave using ESPRIT in the direction estimation unit 520A based on the multiple combined signals restored by the restoration unit 510A. Note that the direction estimation unit is not limited to one that estimates the arrival direction of the desired wave using ESPRIT. The direction estimation unit may be any unit that estimates the direction of arrival of a desired wave based on a plurality of combined signals generated based on received signals of a plurality of antenna elements to which radio waves are input. For example, the direction estimation unit may estimate the direction of arrival of a desired wave using MUSIC (Multiple Signal Classification), or may use a trained model that learns, as training data, a data set that includes the direction of arrival of the desired wave and a plurality of combined signals that are generated based on received signals of a plurality of antenna elements to which the desired wave is input and have information on the phase of each received signal, and estimates the direction of arrival of a desired wave based on input of a plurality of combined signals.

[0036] As described above, the first control unit 300A according to the first embodiment includes the signal extraction unit 310A that extracts a first pulse signal from a signal received by the first antenna 101 to which radio waves are input and that extracts a second pulse signal from a signal received by the second antenna 102 that is disposed at a distance from the first antenna 101 and to which radio waves are input, and the signal combining unit 320A that generates a first combined signal obtained by combining a plurality of first pulse signals in the time axis direction and a second combined signal obtained by combining a plurality of second pulse signals in the time axis direction. As a result, when estimating the direction of arrival of radio waves based on the first combined signal and the second combined signal, the first control unit 300A can improve the accuracy of estimating the direction of arrival of radio waves compared to estimating the direction of arrival of radio waves without generating the first combined signal and the second combined signal.

[0037] Furthermore, the radio wave arrival direction estimation system 1 according to the first embodiment includes a signal line L1 for connecting the signal combining unit 320A and the direction estimation unit 520A so that information can be transmitted between them, a compression unit 330A that is arranged closer to the signal combining unit 320A than the signal line L1 and that compresses the information transmitted by the signal line L1, and a restoration unit 510A that is arranged closer to the direction estimation unit 520A than the signal line L1 and that restores the information compressed by the compression unit 330A. This makes it possible for the radio wave arrival direction estimation system 1 to reduce the amount of information transmitted from the signal combining unit 320A to the direction estimation unit 520A and to simplify the configuration of the input / output interface between the first control unit 300A and the second control unit 500A and the signal line L1.

[0038] In the first embodiment, the first control unit 300A and the second control unit 500A are described as being independent information processing devices, but this is not limited to this. The first control unit may have some of the functions of the second control unit, the second control unit may have some of the functions of the first control unit, the first control unit and the second control unit may be integrally formed, or the first control unit and the second control unit may be treated as a single information processing device.

[0039] In addition, in the first embodiment, the first control unit 300A is configured to output information compressed by the compression unit 330A to the second control unit 500A, but this is not limiting, and the first control unit 300A may be configured to output the multiple combined signals generated by the signal combiner from the signal combiner to the direction estimation unit without compressing them. Furthermore, when the first control unit is configured to output the multiple combined signals generated by the signal combiner from the signal combiner to the direction estimation unit without compressing them, the array antenna may have two antenna elements.

[0040] Furthermore, in the first embodiment, the signal combiner 320A is configured to generate a combined signal in which N pulse signals extracted by the signal extractor are combined in the time axis direction, where N is a preset integer of 2 or greater. However, this is not limited to this. N is not limited to a preset number and may be a number set based on the pulse width of the extracted pulse signals, for example. Specifically, N may be a number calculated by the signal combiner as a value that makes the pulse width of the combined signal equal to or greater than a preset threshold. Alternatively, the radio wave arrival direction estimation system may be configured to not generate a combined signal by the signal combiner but to perform subsequent processing using the pulse signals extracted by the signal extractor when the pulse width of the pulse signals extracted by the signal extractor is equal to or greater than a preset threshold.

[0041] Furthermore, in the first embodiment, the direction estimator 520A is configured to estimate the direction of arrival of the desired wave based on information about the phase of each combined signal input from the restoration unit 510A, for example, a phase difference, but this is not limiting. The direction estimator may be configured to estimate the direction of arrival of the desired wave based on each combined signal input from the restoration unit, and the direction estimator may be configured to estimate the direction of arrival of the desired wave based on information about the strength of each combined signal input from the restoration unit, for example, an intensity difference (amplitude difference).

[0042] Second Embodiment Next, a radio wave arrival direction estimation system 2 according to a second embodiment will be described with reference to Fig. 8. Fig. 8 is a block diagram showing a schematic configuration of the radio wave arrival direction estimation system 2 according to the second embodiment. The radio wave arrival direction estimation system 2 according to the second embodiment differs from the radio wave arrival direction estimation system 1 according to the first embodiment in that the first control unit and the second control unit are connected to each other by an optical transmission unit, but the other configurations are the same, and the same names and symbols as those in the first embodiment will be used and descriptions thereof will be omitted.

[0043] 8, the radio wave direction estimation system 2 according to the second embodiment includes an array antenna 100, an ADC 200, a first control unit 300B, an optical transmission unit 400B, and a second control unit 500B, which are connected to each other via signal lines so as to be able to transmit information. The first control unit 300B, which serves as a signal processing device, includes a signal extraction unit 310A, a signal combination unit 320A, and a compression unit 330B.

[0044] The compressor 330B generates multiple compressed signals, which are signals obtained by compressing multiple combined signals, which are information input from the signal combiner 320A. For example, the compressor 330B generates K compressed signals corresponding to the M combined signals obtained by compressing the number of information transmission paths, and matrix value data indicating the correlation between these M combined signals. In other words, the compressor 330B generates K+1 signals, each consisting of a first compressed signal, a second compressed signal, ..., a Kth compressed signal obtained by compressing the number of information transmission paths, and matrix value data indicating the correlation between these M combined signals. The compressor 330B outputs the generated K+1 signals to the optical transmission unit 400B.

[0045] The optical transmission unit 400B connects the first control unit 300B and the second control unit 500B to each other, and enables information to be transmitted from the first control unit 300B to the second control unit 500B via RoF (Radio over Fiber). The optical transmission unit 400B includes a digital-to-analog converter (hereinafter referred to as DAC) 410B, a transmitter 420B, an optical fiber 430B, a receiver 440B, and an ADC 450B.

[0046] The DAC 410B includes a first DAC 411B, a second DAC 412B, ..., a K-th DAC 41KB. The first DAC 411B, the second DAC 412B, ..., the K-th DAC 41KB convert the first compressed signal, the second compressed signal, ..., the K-th compressed signal, which are digital signals generated by the compressor 330B, into analog signals for transmission via the optical fiber 430B.

[0047] The transmitting unit 420B includes a first optical analog transmitting unit 421B, a second optical analog transmitting unit 422B, ..., a Kth optical analog transmitting unit 42KB, and an optical digital transmitting unit 42(K+1)B. The first optical analog transmitting unit 421B, the second optical analog transmitting unit 422B, ..., the Kth optical analog transmitting unit 42KB, and the optical digital transmitting unit 42(K+1)B each convert the analog signal from the DAC 401B and the matrix-valued data, which is the digital signal from the compressing unit 330B, into an optical signal and output it to the optical fiber 430B. For example, the first optical analog transmitting unit 421B, the second optical analog transmitting unit 422B, ..., the Kth optical analog transmitting unit 42KB, and the optical digital transmitting unit 42(K+1)B each include a light source and an optical modulator that modulates the light from the light source, and converts the electrical signal into an optical signal and outputs it using an external modulation method that modulates the light from the light source in accordance with the information to be output. The transmitter may be configured to convert an electrical signal into an optical signal by a direct modulation method and output the optical signal.

[0048] The optical fiber 430B includes a first optical fiber 431B, a second optical fiber 432B, ..., a K+1-th optical fiber 43(K+1)B. In the optical fiber 430B, the first optical fiber 431B, the second optical fiber 432B, ..., the K+1-th optical fiber 43(K+1)B transmit information input from the first optical analog transmitting unit 421B, the second optical analog transmitting unit 422B, ..., the K-th optical analog transmitting unit 42KB, and the optical digital transmitting unit 42(K+1)B, respectively, to the receiving unit 440B.

[0049] The receiving unit 440B includes a first optical receiving unit 441B, a second optical receiving unit 442B, ..., a K+1th optical receiving unit 44(K+1)B. The first optical receiving unit 441B, the second optical receiving unit 442B, ..., the K+1th optical receiving unit 44(K+1)B convert the optical signals transmitted by the first optical analog transmitting unit 421B, the second optical analog transmitting unit 422B, ..., the Kth optical analog transmitting unit 42KB, and the optical digital transmitting unit 42(K+1)B into electrical signals and output the electrical signals. For example, the first optical receiving unit 441B, the second optical receiving unit 442B, ..., the K+1th optical receiving unit 44(K+1)B each convert the optical signals transmitted by the optical fiber 430B into electrical signals using a photodiode.

[0050] The ADC 450B has a first ADC 451B, a second ADC 452B, ..., a K-th ADC 45KB. The first ADC 451B, the second ADC 452B, ..., the K-th ADC 45KB convert analog signal information input from the first optical receiving unit 441B, the second optical receiving unit 442B, ..., the K-th optical receiving unit 44KB into digital signals and output the digital signals.

[0051] The second control unit 500B as a signal processing device includes a restoration unit 510B and a direction estimation unit 520B. The restoration unit 510B as an information acquisition unit is connected to the ADC 450B and the K+1 optical receiving unit 44(K+1)B, and restores the information compressed by the compression unit 330B based on the digital signal input from the ADC 450B and the information input from the K+1 optical receiving unit 44(K+1)B. The digital signal input from the ADC 450B includes information on the M combined signals output from the signal combining unit 320A, and the information input from the K+1 optical receiving unit 44(K+1)B is matrix value data indicating the correlation of these M combined signals generated by the compression unit 330B. The restoration unit 510B acquires the M combined signals output from the signal combining unit 320A based on this information.

[0052] With this configuration, the signal combining unit 320A and the direction estimating unit 520B according to the second embodiment are connected to each other via the compressing unit 330B, the optical transmitting unit 400B, and the restoring unit 510B so as to be able to transmit information to each other. In other words, the signal combining unit 320A and the direction estimating unit 520B according to the second embodiment are indirectly connected to each other via the optical transmitting unit 400B so as to be able to transmit information to each other. Note that the hardware configurations of the first control unit 300B and the second control unit 500B are similar to that of the first control unit 300A according to the first embodiment, and therefore description thereof will be omitted. Furthermore, the first control unit or the second control unit may have part of the configuration of the optical transmitting unit.

[0053] As described above, the radio wave direction estimation system 2 according to the second embodiment includes the optical transmission unit 400B as an optical transmission path for connecting the signal combining unit 320A and the direction estimation unit 520B so that information can be transmitted between them, the compression unit 330B arranged closer to the signal combining unit 320A than the optical transmission unit 400B and configured to compress information transmitted by the optical transmission unit 400B, and the restoration unit 510B arranged closer to the direction estimation unit 520B than the optical transmission unit 400B and configured to restore the information compressed by the compression unit 330B. With this configuration, the radio wave direction estimation system 2 according to the second embodiment can simplify the configuration of the input / output interface between the first control unit 300B and the optical transmission unit 400B, the input / output interface between the optical transmission unit 400B and the second control unit 500B, and the optical transmission unit 400B.

[0054] Furthermore, for example, by using the compression unit 330B to compress the number of information transmission systems transmitted from the signal combining unit 320A to the direction estimation unit 520B and simplifying the configuration of the optical transmission unit 400B, it becomes possible to reduce the number of elements in each configuration of the optical transmission unit 400B, and to reduce the size, occupied area, and occupied volume of the transmission path.

[0055] Third Embodiment Next, a radio wave arrival direction estimation system 3 according to a third embodiment will be described with reference to Fig. 9. Fig. 9 is a block diagram showing a schematic configuration of the radio wave arrival direction estimation system 3 according to the third embodiment. The radio wave arrival direction estimation system 3 according to the third embodiment differs from the radio wave arrival direction estimation system 2 according to the second embodiment in the configuration of the optical transmission unit, but the other configurations are the same, and the same configurations as those in the second embodiment are assigned the same names and symbols as those in the second embodiment, and the description thereof will be omitted.

[0056] 9, the radio wave direction estimation system 3 according to the third embodiment includes an array antenna 100, an ADC 200, a first control unit 300B, an optical transmission unit 400C, and a second control unit 500B, which are connected to each other via a signal line so as to be able to transmit information. The optical transmission unit 400C, which serves as an optical transmission path, includes a transmitter 420C, an optical fiber 430B, and a receiver 440B.

[0057] The transmitting unit 420C has a first optical digital transmitting unit 421C, a second optical digital transmitting unit 422C, ..., an optical digital transmitting unit 42(K+1)C. The transmitting unit 420C has a first optical digital transmitting unit 421C, a second optical digital transmitting unit 422C, ..., an optical digital transmitting unit 42(K+1)C. The first optical digital transmitting unit 421C, the second optical digital transmitting unit 422C, ..., an optical digital transmitting unit 42(K+1)C each converts the information input from the compressing unit 330B into an optical signal and outputs it to the optical fiber 430B.

[0058] As described above, in the radio wave direction estimation system 3 according to the third embodiment, the optical transmission unit 400C transmits information from the compression unit 330B to the second control unit 500B without converting it into an analog signal. This makes it possible to reduce the area and volume occupied by the optical transmission unit 400C by omitting the DAC and ADC in the optical transmission unit. Note that in the radio wave direction estimation system according to the third embodiment, the first control unit or the second control unit may have part of the configuration of the optical transmission unit.

[0059] Fourth Embodiment Next, a radio wave arrival direction estimation system 4 according to a fourth embodiment will be described with reference to Fig. 10. Fig. 10 is a block diagram showing a schematic configuration of the radio wave arrival direction estimation system 4 according to the fourth embodiment. The radio wave arrival direction estimation system 4 according to the fourth embodiment differs from the radio wave arrival direction estimation system 3 according to the third embodiment in the configuration relating to the transmission of information from the compression unit to the restoration unit, but the other configurations are the same, and the same names and symbols as those in the third embodiment will be used and descriptions thereof will be omitted.

[0060] 10 , the radio wave arrival direction estimation system 4 according to the fourth embodiment includes an array antenna 100, an ADC 200, a first control unit 300D, an optical transmission unit 400D, and a second control unit 500D, which are connected to each other via signal lines so as to be able to transmit information. The first control unit 300D includes a signal extraction unit 310A, a signal combination unit 320A, and a compression unit 330D.

[0061] The compressor 330D compresses the combined signal, which is information input from the signal combiner 320A. For example, the compressor 330D compresses the information input from the signal combiner 320A by converting the M combined signals generated by the signal combiner 320A into matrix value data indicating the correlation between these combined signals using PAST. The compressor 330D outputs the information obtained by the compression to the optical transmission unit 400D.

[0062] The optical transmission unit 400C serving as an optical transmission path includes a transmitter 420C, an optical fiber 430B, and a receiver 440B. The transmitter 420C converts the information input from the compressor 330D into an optical signal and outputs it to the optical fiber 430D. The optical fiber 430D transmits the information input from the transmitter 420D as an optical signal to the receiver 440D. The receiver 440D converts the optical signal transmitted by the optical fiber 430D into electrical signal information and outputs it.

[0063] The second control unit 500D includes a restoration unit 510D and a direction estimation unit 520D. The restoration unit 510D, which serves as an information acquisition unit, restores the information compressed by the compression unit 330D based on information input from the receiving unit 440D. For example, if the information input from the receiving unit 440D is matrix value data indicating the correlation between M combined signals generated by the signal combining unit 320A, the restoration unit 510D acquires the M combined signals generated by the signal combining unit 320A based on the matrix value data. The direction estimation unit 520D estimates the direction of arrival of the desired wave based on the information restored by the restoration unit 510D. Note that the function of the direction estimation unit 520D is similar to that of the direction estimation unit 520B according to the second embodiment, and therefore a description thereof will be omitted. Furthermore, the hardware configurations of the first control unit 300D and the second control unit 500D are similar to those of the first control unit 300A according to the first embodiment, and therefore a description thereof will be omitted.

[0064] In this way, in the radio wave arrival direction estimation system 4 according to the fourth embodiment, the compression unit 330D converts the M combined signals generated by the signal combining unit 320A into matrix value data indicating the correlation between these combined signals, thereby making it possible to reduce the number of elements in each configuration of the optical transmission unit 400D and to reduce the size, occupied area, and occupied volume of the transmission path.

[0065] In addition, the present disclosure allows for free combination of the respective embodiments, modification of any of the components of the respective embodiments, or omission of any of the components of the respective embodiments.

[0066] A signal processing device according to the present disclosure can be used, for example, in a system that estimates the direction of arrival of radio waves based on a signal from an array antenna to which the radio waves are input.

[0067] 1 Radio wave arrival direction estimation system, 2 Radio wave arrival direction estimation system, 3 Radio wave arrival direction estimation system, 4 Radio wave arrival direction estimation system, 10M Mth antenna, 31MA Mth signal extraction unit, 32MA Mth signal combination unit, 42(K+1)B Optical digital transmission unit, 42KB Kth optical analog transmission unit, 43(K+1)B K+1th optical fiber, 44(K+1)B K+1th optical receiving unit, 44KB Kth optical receiving unit, 100 Array antenna, 101 First antenna, 102 Second antenna, 300A First control unit (signal processing device), 300B First control unit (signal processing device), 300D First control unit (signal processing device), 310A Signal extraction unit, 311A ​​First signal extraction unit, 312A Second signal extraction unit, 320A Signal combination unit, 321A First signal combination unit, 322A Second signal combination unit, 330A Compression unit, 330B Compression unit, 330D Compression unit, 400B Optical transmission unit, 400C Optical transmission unit, 400D Optical transmission unit, 420B Transmitting unit, 420C Transmitting unit, 420D Transmitting unit, 421B First optical analog transmitting unit, 421C First optical digital transmitting unit, 422B Second optical analog transmitting unit, 422C Second optical digital transmitting unit, 430B Optical fiber, 430D Optical fiber, 431B First optical fiber, 432B Second optical fiber, 440B Receiving unit, 440D Receiving unit, 441B First optical receiving unit, 442B Second optical receiving unit, 500A Second control unit (signal processing device), 500B Second control unit (signal processing device), 500D Second control unit (signal processing device), 510A Restoring unit (information acquiring unit), 510B Restoring unit (information acquiring unit), 510D Restoration unit (information acquisition unit), 520A direction estimation unit, 520B direction estimation unit, 520D direction estimation unit, 201 first ADC, 202 second ADC, 451B first ADC, 452B second ADC, 411B first DAC, 412B second DAC, L1 signal line, P1 pulse signal, PA coupled signal, W1 pulse width.

Claims

1. A signal processing device comprising: a signal extraction unit that extracts a first pulse signal from a signal received by a first antenna to which radio waves are input, and extracts a second pulse signal from a signal received by a second antenna that is located at a distance from the first antenna and to which the radio waves are input; and a signal combination unit that generates a first combined signal by combining multiple first pulse signals in the time axis direction, and a second combined signal by combining multiple second pulse signals in the time axis direction.

2. The signal processing device according to claim 1, further comprising a direction estimation unit that estimates the direction of arrival of the radio wave based on the first combined signal and the second combined signal.

3. A signal processing device according to claim 2, characterized in that it comprises: a signal line for connecting the signal coupling unit and the direction estimation unit so that information can be transmitted between them; a compression unit that is arranged closer to the signal coupling unit than the signal line and compresses information transmitted by the signal line; and a restoration unit that is arranged closer to the direction estimation unit than the signal line and restores information compressed by the compression unit.

4. The signal processing device according to claim 3, wherein the signal line is an optical transmission line that transmits information as an optical signal.

5. A signal processing device according to claim 3 or 4, characterized in that the signal extraction unit and the signal combination unit perform processing to combine pulse signals for each information transmission system formed for each of a plurality of antennas including the first antenna and the second antenna, and the compression unit compresses the number of information transmission systems, thereby compressing the information transmitted by the signal line.

6. A signal processing method performed by a device having a signal extraction unit and a signal combination unit, comprising the steps of: the signal extraction unit extracting a first pulse signal from a signal received by a first antenna to which radio waves are input; and extracting a second pulse signal from a signal received by a second antenna that is disposed at a distance from the first antenna and to which the radio waves are input; and the signal combination unit generating a first combined signal by combining multiple first pulse signals in the time axis direction, and a second combined signal by combining multiple second pulse signals in the time axis direction.

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